Puzzles and other handcraft construction elements of various kinds have long been known. These consist of a variety of elements arranged for interengagement to form two- or three-dimensional structures generally having a continuous picture on the surface thereof.
The most common puzzles consist of a number of unique elements, i.e., each puzzle element is different from the others. There are also known from U.K. Patent No. 1,378,942 flat snap-fit elements of different geometrical shapes defining alternating protrusions and recesses for interlocking to form a variety of three-dimensional objects. These pieces are relatively rigid and form structures having protruding edges extending from the outer surface.
There is also known a constructed paper element in Japanese origami paper folding which comprises a polygonal element defining two pointed flaps and two pockets on one side thereof. A flap of one such element can be inserted into the pocket of a second such element and, in this way, a two- or three-dimensional structure can be built.
These paper elements suffer from several disadvantages. First, since the pockets only appear on one side surface of the element, not both surfaces, coupling of another element thereto can only be accomplished on one side, i.e., only one side is functional. Second, since they are made of paper, the elements are relatively fragile and structures made therefrom are not very stable. Furthermore, they wear very rapidly so are not suitable for building more than a single structure. In other words, a structure cannot be built, taken apart, and the elements reused to build different structure. Third, these elements, by definition, are designed to be created by hand and are not suitable for mass production. And fourth, no locking mechanism is provided, so the elements often inadvertently slide apart from one another during the construction process.